Control method for moving racks

ABSTRACT

Several embodiments of moveable partitions and controls that permit smooth operation and parallel movement even when they are trackless and that provide safety in operation in avoiding encounters with unexpected objects without unnecessarily stopping the operation when an object is not actually there.

BACKGROUND OF INVENTION

[0001] This invention relates to a method of controlling the movement ofa moveable partition having at least a pair of transversely spaced,ground engaging drive elements for moving the partition along a parallelpath.

[0002] Moveable partitions are used for many applications. For exampleone type of partition is a storage rack on which a variety of articlesare placed. Frequently a plurality of these racks are positioned in aspecific storage area. However fixed racks require more space than isacceptable in many applications.

[0003] It has been proposed, therefore, to mount the racks or partitionson rails by means of wheels so they can be moved into an abuttingrelation to free up space when access is not required to add or removearticles from a given rack. Then when access is required one or moreracks may be moved to create an access aisle. In fact it also has beenproposed to power the racks for such movement.

[0004] However the use of tracks requires a dedicated area and adds tothe cost. Therefore it has been proposed by application's assignee touse a plurality of caterpillar like drive belts to support and move thepartitions or racks and thus eliminate the need for guide rails. Howeverwhen the racks have substantial width, a plurality of belts are requiredand at least some of them must be driven if they are to be powered andalso to try to maintain parallel movement. Such an arrangement is shownin the assignee's co-pending application Ser. No. 10/248,686, filed Feb.9, 2003.

[0005] Even then, however, there is a possibility for the rack to strayfrom its intended course for a variety of reasons. To try to minimizesuch undesired straying from the intended path, the aforenotedapplication synchronizes all of the drives by providing a common driveshaft that interconnects all drives. However even when this is done suchfactors subtle displacement of the moving track after repeatedreciprocating movements which may accumulate to an unacceptable level.Also, unbalanced loading of storage articles or mechanical errors maycause the rack may move with inclination with respect to the desiredtraveling direction.

[0006] This problem can even occur with a movable rack that is guided byrails. Again such factors as unbalanced loading of storage articles,variation in machining accuracy of parts of the drive section can resultin a large load because of friction between wheels and rails. This cancause uneven or jerky movement along the rails.

[0007] It is therefore an object of this invention to provide a controlmethod for a moving rack capable of moving without displacement in itsmoving path after repeated reciprocating movements and capable ofeliminating oblique movement and meandering movement in spite ofunbalanced loading of storage articles, mechanical working errors, orthe like.

SUMMARY OF INVENTION

[0008] This invention relates to a moveable partition and method ofcontrolling its movement. The partition has at least a pair oftransversely spaced, ground engaging drive elements for moving thepartition along a parallel path.

[0009] The method comprises the steps of sensing the path of movement ofthe partition and controlling the drive elements to maintain a parallelpath of movement.

[0010] The partition has a control that senses the path of movement ofthe partition and controls the drive elements to maintain a parallelpath of movement.

[0011] In accordance with another feature of the invention, a structureof the type described above is operated to maintain the parallel controlonly if the path of movement deviated from parallel by more than apredetermined amount.

[0012] In accordance with a still further feature of the invention thepreviously described structure has a position sensor for determiningthat an undesired object is between two partitions and the movement ofthe partitions is stopped but only after correction of the position ofone partition has been accomplished.

BRIEF DESCRIPTION OF DRAWINGS

[0013]FIG. 1 is a top plan view of one end of a partition mounting baseconstructed and controlled in accordance with the invention.

[0014]FIG. 2 is a longitudinal cross sectional view of the end shown inFIG. 1.

[0015]FIG. 3 is a top plan view of the central portion of the partitionmounting base.

[0016]FIG. 4 is a longitudinal cross sectional view of the portion shownin FIG. 3.

[0017]FIG. 5 is a top plan view of the other end of the partitionmounting base.

[0018]FIG. 6 is a longitudinal cross sectional view of the end shown inFIG. 5.

[0019]FIG. 7 is a transverse cross sectional view of both of thepartition mounting base ends.

[0020]FIG. 8 is a transverse cross sectional view of the central portionof the partition mounting base ends.

[0021]FIG. 9 is an enlarged cross sectional view looking in the samedirection as FIGS. 2 and 5 taken through the axis of the base drive.

[0022]FIG. 10 is a perspective view of a sensor used in connection withthe invention.

[0023]FIG. 11 is a top plan view of a moveable panel utilizing thesensor of FIG. 10 in one course of control.

[0024]FIG. 12 is a top plan view, in part similar to FIG. 11 showing themoveable panel in another course of control.

[0025]FIGS. 13a, 13 b and 13 c are schematic top plan views showingvarious control conditions that may exist in panel movement.

[0026]FIG. 14 is a graphical view showing the various control judgmentsmade to maintain parallel panel movement.

[0027]FIGS. 15a, 15 b and 15 c are in part similar to FIGS. 13a, 13 band 13 c and are schematic top plan views showing various controlconditions that may exist in panel movement.

[0028]FIG. 16 is a graph showing how the control parameters aredetermined.

[0029]FIGS. 17a, 17 b and 17 c are in part similar to FIGS. 13a, 13 band 13 c and FIGS. 15a, 15 b and 15 c and are schematic top plan viewsshowing other control conditions that may exist in panel movement andutilizing a different sensor arrangement.

[0030]FIG. 18 is a graph showing how the control parameters aredetermined.

[0031]FIGS. 19a, 19 b and 19 c are in part similar to FIGS. 17a, 17 band 17 c are schematic top plan views showing other control conditionsthat may exist in panel movement and utilizing the different sensorarrangement FIG. 20 is a graph showing how the control parameters aredetermined.

[0032]FIG. 21 is a front elevational view of a rack constructed andoperated in accordance with another embodiment of the invention.

[0033]FIG. 22 is a partially perspective view of the sensor arrangementshown in FIG. 21.

[0034]FIG. 23 is a front elevational view in part similar to FIG. 21 andshows another embodiment that utilizes a contact type sensor.

[0035]FIG. 24 is a side elevational view of this embodiment showing howa plurality of racks can employ the invention and shows the racksconverged relative to each other.

[0036]FIG. 25 is a top plan view showing the locations of the positionsensors.

[0037]FIG. 26 is an enlarged front elevational view showing the positionsensor.

[0038]FIG. 27 is a side elevational view showing the position sensors.

[0039]FIG. 28 is a further enlarged view of the position sensor showingit in a normal position in solid lines and in displaced positions inphantom lines.

[0040]FIG. 29 is an electrical diagram for explaining how the positionsensor provides an output signal.

[0041]FIG. 30 is a top plan view of a partition system constructed andoperated in accordance with another embodiment of the invention.

[0042]FIG. 31 is an enlarged view of the area in the circle 31 in FIG.30.

[0043]FIG. 32 is an enlarged view of the area in the circle 32 in FIG.30.

[0044]FIG. 33 is a top plan view, in part similar to FIG. 30,and shows astill further embodiment.

DETAILED DESCRIPTION

[0045] Unknown;Referring now in detail to the drawings and initially toFIGS. 1-10, a moveable drive base for a partition which may comprise,for example a storage rack, indicated generally at 51, is comprised of abase frame,indicated generally at 52, and fabricated from a suitablematerial such as metal plates, made of iron or the like and bent in theshape of a letter U or L in section, assembled in a frame-like shape.The base frame 52 contains and supports assembled running wheel shafts,their rotational drive mechanisms, and the like to be described in moredetail shortly.

[0046] The base frame 52 has a considerably long length as compared toits width. Supported at its ends and in its central portion are pairs oftransversely extending saddles 53 formed in the shape of an invertedcharacter “Ω” viewed from the side. Bearings or pillow blocks 54 arefixed between the saddles 53. The end pair of bearings 54 journal driveshafts 55. Parallel to these drive shafts 55, follower shafts 56 arejournalled by these pairs of bearings 54.

[0047] At the outer ends of the frame 52, a drive wheel 57 is fixed toeach of the drive shafts 55 between the pair of saddles 53, as best seenin FIG. 7. To power each of the drive shaft 55, a gear 58 is fixed atthe outer side of one of the saddles 53. An electric drive motor 59 isfixed through an appropriate support member adjacent each of the gears.A pinion 61 is fixed to the output shaft of the motor 59 and the pinionmeshes with the gear 58 to drive it and the drive wheel 57. Preferablythe motor 59 has an integral transmission for reducing the rotationalspeed of the motor 59 and the output is further reduced by the pinion 61and gear 58 to provide more driving power.

[0048] As seen in FIG. 7, the follower shaft 56 is disposed parallel tothe drive shaft 55 in the direction of travel of the moving rack 51. Afollower wheel 62 is fixed to the follower shaft 56 between the pair ofsaddles 53. The follower wheel 62 has the same diameter as the drivewheel 57.

[0049] A belt-like endless track member 63 is entrained around the drivewheel 57 and the follower wheel 62. The endless track member 63 is incontact with the surface of a floor 64 upon which the moving rack 51supported. Thus when the drive motors 59 are operated the belts willdrive the partition 51 along the floor 64 through the operation of thetrack members 63.

[0050] Although they are not powered, similar belt track member 63 andsupporting wheels along with bearings and shafts are positioned atselective places along the frame assembly 52 to support the weight ofthe partition between the driven ones at the ends of the frame assemblyas shown in FIGS. 3, 4 and 8. Because the structures are otherwise thesame as the driven ones like reference numerals have been utilized todesignate like parts. For this reason it is not believed necessary tofurther describe these additional supporting arrangements A controlcircuit and circuit board, indicated by the reference numeral 65, andshown in FIGS. 1 and 2 is mounted at one end of the frame assembly 52for controlling the operation of the motors 59. This structure and themethod by which it operates will be described in detail later.

[0051] Thus as described above, the endless track member 63 is wrappedaround the outer circumferential surfaces of the drive wheel 57 andfollower wheel 62, so that the drive wheel 57 and follower wheel 62 areconnected by the endless track member 63. The drive wheel 57 is drivenfor rotation by the motor 59 both in forward and reverse directions, sothe moving rack 51 runs on the floor 64. The non-driven pair of followerwheels 62 and the endless track member 63 wrapped around these followerwheels 62 as shown in FIGS. 3, 4 and 8 thus also rotate when the movingrack 51 is moved.

[0052] Preferably the endless track member 63 wrapped around the outercircumferential surfaces of the drive wheel 57 and follower wheel 62 ofthe driven and non-driven pairs are toothed belts to prevention ofsliding over the drive wheel 57 or the follower wheel 62, and the drivewheel 57 and the follower wheel 62 are wheels each having complimentarygrooves into which the teeth of the track member 63 are fitted. Even so,however, there is a possibility that the endless track member 63 will bedisplaced in the axial direction with respect to the drive wheel 57 andfollower wheel 62. Therefore it is desirable that some kind ofdisplacement prevention means is provided. This could be done byproviding flanges on both edges of the drive wheel 57 and follower wheel62. However, in a system in which the endless track member 63 is incontact with the floor surface as in this invention, the amount ofprojection of the flanges must be smaller than the thickness of theendless track member 63. This may not be sufficient to prevent axialdisplacement of the endless track member 63.

[0053] Therefore the structure shown in FIG. 9 is preferably adopted asa displacement prevention measure of the endless track member 63. Asseen there, the underside of the base frame 52 of the moving rack arefixed L shaped angle members 67 one side of which extends verticallydownwardly along the side surface of the endless track member 63. Suchangle members 67 are fixed in a pair, with one side each of these anglemembers 67 along the side surfaces of the endless track member 63. Thepair of angle members 67 may run along both sides of the drive wheel 57and/or follower wheel 62.

[0054] Since the endless track mechanisms 63 cause the moving rack 51 torun in the direction of the endless track member 63, the moving rack 51can be moved in a straight line in the direction perpendicular to itsfront face. Therefore, the moving rack 51 may be placed directly on thefloor surface, and guide rails need not employed. That is, a rail-lessmoving rack is achieved. Also, because the load of the moving rack 51itself and the load exerted on the moving rack by articles stored in themoving rack are supported by the running track mechanisms includingthose that are not driven, the load exerted on a unit area of the floorbecomes small, so that the moving rack can be installed without need offloor reinforcement.

[0055] However a problem may arise that other factors, examples of whichwill be given later may cause the rack 51 to travel in a less thanparallel path and one that may become skewed. To avoid this it has beenproposed in commonly assigned application Ser. No. 10/248,686, filedFeb. 9, 2003, to connect all of the drive shafts to each other so as tomove the rail-less rack in a straight line. However, because of errorsin the working accuracy of parts, unbalanced loading of storagearticles, and the like, the moving track can be displaced subtly uponsuccessive movement or the moving rack can move obliquely ormeanderingly.

[0056] Thus, in this invention, drive mechanisms each having a drivewheel 57 and an endless track member 63 are provided independently onboth the ends of the moving rack 51. Displacement with respect to areference body extending in the moving direction of the moving rack 51is detected by a sensor provided on the moving rack 51, and the separatedrive mechanisms, and specifically their drive motors 59, are controlledindependently in response to the displacement detected. This allows themoving rack 51 to reciprocate following a defined path at all times.

[0057]FIG. 10 shows an example of an optical sensor unit for use as asensor in this invention. As seen in FIG. 10, a guide pattern 68 ismarked on the surface of a floor on which a moving rack 51 is installedas a reference body for detecting the displacement of the moving rack.The guide pattern 68 is made of a material having a high contrast withrespect to the floor surface on which it is marked, or of a materialhaving a high light reflectivity compared to that of the floor surface.The guide pattern 68 may be marked with paint, or may be a tape affixedto the floor. Alternatively a steel plate or the like may be used. Inany event, the guide pattern 68 should have clear edges on both sides.

[0058] A sensor unit, indicated generally at 69, is disposed above theguide pattern 68 in an opposing relation. The sensor unit 69 has a pairof light sources 71 and 72, which are adapted to illuminate the guidepattern 68 near its outer edges. The light sources 71 and 72 may be, forexample, lamps, LEDs or the like.

[0059] The sensor unit 69 also has a pair of light receiving elements 73and 74. The light receiving elements 73 and 74 receive the reflectedlight from the guide pattern 68 near its edges. The light sources 71 and72 are disposed to illuminate the light receiving areas of the lightreceiving elements 73 and 74, respectively. For the light receivingelements 73 and 74, photodiodes, phototransistors, solar batteries andother appropriate light sensitive elements can be used.

[0060] Referring now to FIGS. 11 and 12, these show schematically theapplication of the sensor 69 to a the rail-less moving rack 51 having astructure of the type shown in FIGS. 1-9. As already noted, the rack 51is provided with endless track members 63 with electric motors 59 astheir drive sources operated independently on both ends. In order todetect the edges of the guide pattern 68 marked in the moving directionof the moving rack 51, two sensor units 69 are disposed at the front andthe rear of the moving rack 51 in its moving direction. Each of thesensor units 69 has light receiving elements 73 and 74 for detecting theedges of the guide pattern 68. The light receiving elements 73 and 74 inthis embodiment are of a type which detects the amount of reflectedlight.

[0061] As also noted previously control means independently control theleft and right motors 59 according to the output of the sensor unit onthe forward side in the moving direction of the moving rack 51 and thatof the sensor unit on the rear side. The control means is incorporatedin the control circuit board 65 (not shown in these figures), and can beconstituted by a circuit including, for example, a microcomputer made upof a microprocessor, a ROM, a RAM and the like. The control operation ofthe control means will be described shortly.

[0062] This embodiment is characterized in that the left and right drivemotors 59 are basically controlled independently according to the outputof the sensor unit 69 on the forward side of the moving rack in themoving direction and the output of the sensor unit 69 on the rear side.In the example shown in FIGS. 11 and 12, by detecting the ratio of theamount of received light of one light receiving element 73 to the amountof received light of the other light receiving element 74 of the sensorunit 69 on the forward side of the moving rack 51 in the movingdirection, the left and right motors 59 are controlled such that a ratioof the amount of received light of one light receiving element 73 to theamount of received light of the other light receiving element 74 of thesensor unit 69 on the forward side of the moving rack 51 in the movingdirection becomes equal.

[0063] The control method will be explained more specifically byreference to FIGS. 13a, 13 b and 13 c along with FIG. 14. First, controlis performed such that the amounts of received light of the lightreceiving elements 73 and 74 of the sensor unit 69 on the forward sidein the moving direction become equal. Here, it is assumed that theamounts of received light of the light receiving elements 73 and 74 areset such that they become equal when both edges of the guide pattern 68cross the centers of the light receiving areas of the light receivingelements 73 and 74.

[0064] For simplicity, in FIGS. 13a, 13 b and 13 c and in FIG. 14, thelight receiving element 73 is designated as “1” and the light receivingelement 74 as “2.” If both the edges of the guide pattern 68 arecrossing the centers of the light received areas of the light receivingelements 1, 2 as shown in FIG. 22a, the outputs of the light receivingelements 1,2 are both moderate, as shown in the column a of FIG. 14,control of the left and right motors 59 need not be corrected and thejudgment is “OK.” Then the control of the left and right motors 59 isequal as shown in FIG. 11.

[0065] However, if the light receiving areas of the light receivingelements 1, 2 are displaced to the right with respect to the guidepattern 68 as shown in FIG. 13b, the light receiving element 1 on theleft side as viewed in the moving direction receives more reflectedlight from the guide pattern 68 while the light receiving element 2 onthe right side receives less reflected light from the guide pattern 68,then the output of the light receiving element 1 becomes “large” andthat of the light receiving element 2 becomes “small,” as shown in thecolumn b of FIG. 14. Since this shows that the moving rack 51 is biasedto the right as viewed in the moving direction. This operation is shownin FIG. 12. The moving rack 51 is moved to the left until the conditionshown in FIG. 13a is achieved, for example, by controlling speeds of theleft and right motors 59 or by temporarily stopping the drive of theright motor 59.

[0066] On the other hand, if the light receiving areas of the lightreceiving elements 1, 2 are displaced to the left with respect to theguide pattern 68 as shown in FIG. 13c, the output of the light receivingelement 1 becomes “small” and that of the light receiving element 2becomes “large,” as shown in the column c of FIG. 14. Since this showsthat the moving rack 51 is biased to the left as viewed in the movingdirection, the moving rack 51 is moved to the right until the conditionshown in column a is achieved, for example, by controlling speeds of theleft and right motors 59 or by temporarily stopping the drive of theleft motor 59.

[0067] In this way, control is performed such that the outputs of thelight receiving elements 1, 2 of the sensor unit on the forward side inthe moving direction have a predetermined value, and then the left andright motors 59 are controlled independently such that the outputs ofthe light receiving elements 1, 2 of the sensor unit on the rear side inthe moving direction coincide with each other.

[0068]FIGS. 15a, 15 b and 15 c and FIG. 16 illustrate how this controlis performed. In conditions shown in FIGS. 15a, 15 b and 15 c, theposition of the moving rack 51 in the lateral direction is controlled asmentioned above, and the outputs of the light receiving elements 1, 2 ofthe sensor unit on the forward side in the moving direction coincidewith each other. In the condition shown in FIG. 15a, the outputs of thepair of light receiving elements 1, 2 of the sensor unit on the rearside in the moving direction also coincide with each other and themoving rack 51 is positioned in a predetermined place, so that ajudgment can be made that oblique movement or meandering movement hasn'toccurred. Therefore, the judgment is “OK” as shown in the column a ofFIG. 16, and control of the left and right motors 59 need not becorrected.

[0069] On the contrary, as shown in FIG. 15b, the pair of lightreceiving elements 1, 2 of the sensor unit 69 on the rear side in themoving direction are displaced to the right with respect to the guidepattern 68 as viewed in the moving direction. In this case, as shown inthe column b of FIG. 16, the output of the light receiving element 51becomes large and that of the light receiving element 2 becomes small,so that a judgment can be made that the moving rack is moving obliquelyto the left. Then, inclination of the moving rack 51 is corrected untilthe condition shown in FIG. 15a is achieved, for example, by controllingspeeds of the left and right motors 59 or by temporarily stopping thedrive of the right motor 59.

[0070] Also, suppose that, as shown in FIG. 15c, the pair of lightreceiving elements 1, 2 of the sensor unit 69 on the rear side in themoving direction are displaced to the left with respect to the guidepattern 68 as viewed from the moving direction. In this case, as shownin the column c in FIG. 16, the output of the light receiving element 1becomes small and that of the light receiving element 2 becomes large,so that a judgment can be made that the moving rack is moving obliquelyto the right. Then, inclination of the moving rack 51 is corrected untilthe condition shown in FIG. 15a is achieved, for example, by controllingspeeds of the left and right motors 59 or by temporarily stopping thedrive of left motor 59.

[0071] As described above, if the left and right motors 59 arecontrolled according to the output of the sensor unit 69 on the rearside in the moving direction, the position of the sensor unit 69 on theforward side in the moving direction with respect to the guide pattern68 is displaced. Thus, the moving rack is controlled to a condition inwhich no oblique movement occurs by repeating the control according tothe output of the forward sensor unit 69 and that according to theoutput of the rear sensor unit 69.

[0072] To summarize regarding the control of the moving rack 51, firstthe outputs of the left and right light receiving elements on theforward side are compared and unless they coincide, the left and rightdrive motors 59 are controlled independently until coincidence isachieved. Then outputs of the left and right light receiving elements onthe rear side in the moving direction are compared; and unless theycoincide, the left and right drive sources are further controlledindependently until coincidence is achieved. In this way, by controllingindependently the left and right drive sources according to the outputsof the light receiving elements on the forward and rear sides in themoving direction, control accuracy is improved and, as a result, obliquemovement and meandering movement is prevented.

[0073] These controls can be performed with appropriate control means,for example, control means constituted by a microcomputer with a centralprocessing unit (CPU), a read only memory (ROM) in which programs arestored, a random access memory (RAM) in which data is stored, and thelike. In such control means, the CPU compares or calculates detectedsignals from the sensors, and the program is designed so that the leftand right drive sources are controlled independently according to theprocessing result of the CPU until the detected outputs of the sensorscoincide.

[0074] Now, description will be made on a variant of the sensor unit,and a control device and a control method for a moving rack using thevariant. Referring first to FIG. 17, first and second light receivingelement groups mounted on the forward side of the moving rack 51 areidentified by the reference numerals 75 and 76. Each of the lightreceiving element groups 75 and 76 is made up of a pair of lightreceiving elements. The light receiving elements of the first lightreceiving element group 75 are designated as 1, 2 and those of thesecond light receiving element group 76 as 3, 4. The light receivingareas of the light receiving elements 1, 2 are in contact with eachother transversely. These light receiving areas lie near the left edgeof the guide pattern 68. On the other hand, the light receiving areas ofthe light receiving elements 3, 4 are also in contact with each otherlaterally, and these light receiving areas lie near the right edge ofthe guide pattern 68.

[0075]FIG. 18 depicts the control parameters utilized in this system andmethod. Column a of FIG. 18 shows the output puts of the light receivingelements 1, 2, 3, 4 when the left edge of the guide pattern 68 is on thecontact point of the light receiving areas of the light receivingelements 1, 2 of the first light receiving element group 75 and the leftedge of the guide pattern 68 is on the contact point of the lightreceiving areas of the light receiving elements 3, 4 of the second lightreceiving element group 76, as shown in FIG. 17a. Here, the amount ofreceived light is differentiated according to whether it is higher thana certain level, in a medium level or lower than the medium level. Theseoutputs are represented by “0” if higher, by “Δ” for a medium level, andby “x” if lower.

[0076] If the outputs of the light receiving elements 1, 2, 3, 4 arerepresented by “x◯◯x,” as shown in the column a of FIG. 18, a judgmentis made that there is no lateral displacement of the moving rack andposition correction control need not be performed.

[0077] On the other hand, where the outputs of the light receivingelements 1, 2, 3, 4 are represented by “Δ◯Δx,” as shown in the column bof FIG. 18, the moving rack 51 is in a condition in which it isdisplaced to the left at the forward side in the moving direction, asshown in FIG. 17b. Then, as in the foregoing control, the moving rack 51is moved to the right until a predetermined position shown in FIG. 17ais achieved, for example, by controlling speeds of the left and rightmotors 59 or by temporarily stopping the drive of the right motor 59.

[0078] On the other hand, in the case where the outputs of the lightreceiving elements 1, 2, 3, 4 are represented by “xΔ◯Δ,” as shown in thecolumn c of FIG. 18, the moving rack is in a condition in which it isdisplaced to the right at the forward side in the moving direction, asshown in FIG. 17c. Then, as in the foregoing control, the moving rack 51is moved to the left until a reference position shown in FIG. 17a isachieved, for example, by controlling speeds of the left and rightmotors 59 or by temporarily stopping the drive of the left motor 59.

[0079] Referring now to FIGS 19 a, 19 b and 19 c, two light receivingelement groups 75 and 76 having the same structure as the foregoingsensor unit are mounted on the rear side of the moving rack 51. A firstlight receiving element group 75 has light receiving elements 1, 2, anda second light receiving element group 76 has light receiving elements3, 4. The light receiving areas of the light receiving elements 1, 2 arein contact with each other laterally and these light receiving areas lienear the left edge of the guide pattern 68. The light receiving areas ofthe light receiving elements 3, 4 are also in contact with each otherlaterally, and these light receiving areas lie near the right edge ofthe guide pattern 68.

[0080] If, as shown in FIG. 19(a), the left edge of the guide pattern 68is on the contact point of the light receiving areas of the lightreceiving elements 1, 2 of the first light receiving element group 75and the right edge of the guide pattern 68 is on the contact point ofthe light receiving areas of the light receiving elements 3, 4 in thesecond light receiving element group 76, outputs of the light receivingelement groups 75 and 76 on the rear side in the moving direction of themoving rack become the same as those of the light receiving elementgroups 75 and 76 on the forward side in the moving direction of themoving rack. At this time, the outputs of the light receiving elements1, 2, 3, 4 of the sensor units 75 and 76 on the rear side in the movingdirection are represented by “x◯◯x,” as shown in the column a of FIG.20, and a judgment is made that the moving rack has a posture withoutoblique movement so that correction control of the left and right motors59 is not needed.

[0081] On the other hand, if, as shown in FIG. 19b, the rear side of themoving rack in the moving direction is displaced to the right withrespect to the moving direction, outputs of the light receiving elements1, 2, 3, 4 on the rear side in the moving direction are represented by“Δ◯Δx” as shown in the column b of FIG. 20. A judgment can be made fromthe outputs that the moving rack is inclined obliquely to the left.Then, control is performed until the reference position shown in FIG.19a is achieved, for example, by controlling speeds of the left andright motors 59 or by temporarily stopping the drive of the right motor59, for the correction of the inclination.

[0082] On the other hand, if as shown in FIG. 19c, the rear side of themoving rack in the moving direction is displaced to the left, outputs ofthe light receiving elements 1, 2, 3, 4 on the rear side in the movingdirection are represented by “xΔ◯Δ” as shown in the column c of FIG. 20.A judgment can be made from the outputs that the moving rack is inclinedobliquely to the right. Then, control is performed formed until thereference position shown in FIG. 19a is achieved, for example, bycontrolling speeds of the left and right motors 59 or by temporarilystopping the drive of the left motor 59, for the correction of theinclination.

[0083] Thus with this embodiment, by the control of the left and rightmotors 59 on the rear side, the light receiving elements 1, 2, 3, 4constituting the light receiving element groups 75 and 76 on the forwardside in the moving direction are displaced from the reference positionwith respect to the guide pattern 68, so that the moving rack iscontrolled to a condition in which no oblique movement occurs byrepeating the control according to the outputs of the forward lightreceiving element groups 75 and 76 and that according to the outputs ofthe rear light receiving element groups 75 and 76. As control means forperforming such control, a microcomputer such as mentioned previouslycan be used.

[0084] In the control method and the control device for a raillessmoving rack having light receiving element groups 75 and 76 as shown inFIG. 17 and FIG. 19, since edges of the guide pattern 68 are observed atall times as to whether they are positioned between paired lightreceiving elements, even slight positional displacement can be detectedfrom the difference in detected outputs from the paired light receivingelements. This allows fine control of the left and right motors 59,thereby correcting positional displacement, oblique movement andmeandering movement of the moving rack within a very small range.

[0085] As thus far described the guide pattern has been on the floor.However the guide pattern may be provided above the moving rack 51, anexample of which is shown in FIG. 21 and FIG. 22. FIG. 21 actually isthe first figure showing the partition structure above the base 52.Since the structure of the base 52 is the same as previously describedexcept for the sensor location, it will not be described further.

[0086] As seen in FIG. 21 and FIG. 22, sensor units 77 are attached on atop plate 78 of the moving rack 51. The construction of the sensor unit77 may be the same as any one of the foregoing embodiments. Above thesensor units 77 are fixed, arranged in the moving direction of themoving rack, hangers 79 that are connected to the ceiling, beams, postsor opposing walls, and other appropriate structural bodies of thebuilding in which the moving rack 51 is installed. A member (not shown)protruding upwardly from the moving rack 51 engages with and moves alongthe hangers 79, to insure that the moving rack 51 will be maintainedupright. The bottom of the hangers 79 faces the sensor unit 77, and aguide pattern 80 of any type as aforedescribed is placed on the bottomof the hanger 79.

[0087] As shown in FIG. 22, the sensor unit 77 has a light emittingsection 81 for emitting illumination light toward the guide pattern 80and a light receiving section 82 for receiving the reflected light ofthe illumination light from the guide pattern 80. The light receivingsection 82 may be made up of a light receiving element of a type fordetecting the amount of reflected light from the guide pattern 80 asshown in FIG. 10 or that of a type for detecting left and right edges ofthe guide pattern 80 as shown in FIG. 17.

[0088] Now, an embodiment using a mechanical sensor as the sensor willbe described with reference to FIG. 23 through FIG. 29. Referring firstto FIG. 23 and FIG. 24, these show the exterior of a moving rackaccording to this embodiment which is again identified generally by thereference numeral 51. The rack 51 has mechanical sensors 83, of a typeto be described later, attached to the top plate 78. Hanger receivers 84fixed in the direction of depth of the moving rack 51 to cover thesensors 83. The hanger receivers 84 channel type members having a hatshape in section.

[0089] A hanger 85 extends through the hanger receiver 84 in thehorizontal moving direction of the moving rack 51. The hanger 85 is madeof a pipe of a rectangular shape in section and is supported byappropriate supporting means (not shown), for example, between a pair offixed racks or by a wall or ceiling of the building in which the movingrack 51 is installed. Typically, a plurality of moving racks 51 arearranged on common hangers 85 so that they can be mover adjacent eachother as shown in FIG. 24 or separated. The hanger 85 extends throughhanger receivers 84 of the moving racks 51 that constitute one unit. Therunning mechanism or the drive mechanism of the moving rack 51 has thesame construction as those shown in FIGS. 1 through 9 previouslydescribed. In FIG. 25 through FIG. 27, the numeral 86 designates a postand numeral 87 a side panel, respectively, of the moving rack 51.

[0090] The construction of the sensor 83 will be described in moredetail particularly by reference to FIGS. 25-27. A base plate 88 isfixed on the top plate 78 of the moving rack 51 and extendshorizontally. Mounted on the base plate 88 are hanger receiver lowermembers 89, each bent in a hat shape, at the forward and rear ends ofthe moving rack 51. These hanger receiver lower members 89 are coveredby both forward and rear ends of the hanger receiver 84. The left andright ends of the hanger receiver lower members 89 and the hangerreceiver 84 are fixed to the base plate 88 by suitable threadedfasteners.

[0091] The hanger 85 passes through spaces surrounded by the hangerreceiver 84 and hanger receiver lower members 89 with a clearancebetween the hanger receiver 84 and hanger receiver lower members 89. Themoving rack 51 usually moves with the hanger receiver 84 and hangerreceiver lower members 89 out of contact with the hanger 85 because thisstructure is provided primarily for safety purposes to prevent falling.However, but if the moving rack 51 becomes inclined by some cause, thehanger receiver 84 or the hanger receiver lower members 89 come incontact with the hanger 85 and the moving rack 51 is prevented fromfalling.

[0092] Window holes 91 (FIG. 27) are formed on one side of the hangerreceiver 84 at positions near the forward and rear ends so that theplacement of the mechanical sensors 83 is not obstructed. For thearrangement of the sensor 83, a pair of support plates 92 rise up acrosseach of the window holes 91 and face each other.

[0093] A variable resistor 93 as a sensor body is fixed to one of thepaired support plates 92, and a rotation control shaft 94 of thevariable resistor 93 is supported for rotation by the other supportplate 92. A lever 95 extends upwardly from the rotation control shaft 94rises up a integrally toward one side of the hanger 85. At the head, orthe top, of the lever 95 is mounted a flat roller 96 for rotation withthe lever 95. The rotation control shaft 94 and the lever 95 are biasedby appropriate biasing means such as a spring or the like to hold theroller 96 in contact with one side of the hanger 85 at all times. Thesesupport plates 92, variable resistor 93 and roller 96 are partiallyexposed to the outside of the hanger receiver 84 through the window dowhole 91. Thus the components including the support plates 92, variableresistor 93, roller 96 and lever 95 constitutes the mechanical sensor83. Sensors 83 are disposed at the front and the rear of the moving rack51.

[0094] Because the mechanical sensor 83 is configured as described, ifthe relative position of the moving rack 51 to the hanger 85 isdisplaced laterally, the distance between the side of the hanger 85 andthe roller 96 changes, resulting in pivotal movement of the lever 95.Thus, the hanger 85 serves as a reference body for detecting thedisplacement of the moving rack. FIG. 28 shows how the lever 95 cam beinclined in either direction. When the moving rack 51 is in a referenceposition with respect to the hanger 85, the lever 95 is adjusted suchthat it has an upright posture as shown in FIG. 28 by solid lines. Ifthe moving rack 51 is biased from the reference position toward theleft, the lever 95 is inclined toward the right in FIG. 28, and if themoving rack 51 is biased from the reference position toward the right,the lever 95 is inclined toward the left in FIG. 28. Because therotational position of the rotation control shaft 94 of the variableresistor 93 changes depending on the inclination of the lever 95, theresistance value of the variable resistor 93 will change.

[0095] As seen in FIG. 29, a certain voltage Vcc is applied to avariable resistor 93 between its terminals to form a potentiometer. Anoutput voltage Vo is be obtained from the variable output terminals inresponse to the position of a moving contact. This output voltage Vo isa detected output of the mechanical sensor 83. When only the outputvoltage Vo is set as a reference when the moving rack 51 is at areference position, if the lever 95 is inclined to the left or the rightas shown in FIG. 28 by broken lines, the output voltage Vo changes froma reference value to a plus or minus one. Thus, the lateral direction inwhich the moving rack 51 is displaced can be detected from changes inthe output voltage Vo, and the motors 59 as the left and right drivesources are controlled independently in response to this detected signalto bring the output voltage Vo into coincidence with a reference value,thereby eliminating positional displacement or oblique movement of themoving rack 51.

[0096] The embodiments thus far described are of a systems in whichdisplacement with respect to a reference body lying in the movingdirection of a moving rack is detected by sensors provided on the rackand in which left and right drive sources are controlled independentlyin response to the displacement detected by the sensors. In such controlmethod, the left and right side drive sources are independentlycontrolled such that, if the rack moves obliquely, the sensors detectthe oblique movement to issue an order to correct it. Therefore, therack moves with little or no oblique movement. However, since controloperations to correct the oblique movement, that is, speed controloperations of the drive wheels provided independently on the left andright sides of the rack are performed separately and at all times, it isconceivable that the rack may jerk in its movement with its left andright sides moving ahead or behind with respect to each other. Toeliminate such a disadvantage, an arrangement may be preferably adoptedsuch as shown in the following embodiment of FIGS. 30-33.

[0097] The arrangement of this embodiment is the same as that in any ofthe foregoing embodiments in that drive wheels and their drive sourcesare provided independently on the left and right sides of the rack. Itis also the same in that displacement with respect to a reference bodyis detected by sensors provided on the moving rack. However, the sensorsare configured to detect the degree of displacement with respect to thereference body to detect the amount of oblique movement of the movingrack.

[0098] In accordance with this embodiment, a control such as a CPU andthe like is arranged such that the left and right drive sources arecontrolled independently at the same rotational speed in a “parallelmovement mode” if the amount of oblique movement detected by the sensorsis within a tolerable range. However the left and right drive sourcesare controlled independently at different rotational speeds to eliminatethe oblique movement in an “oblique movement correction mode” if theamount of oblique movement detected by the sensors is beyond thetolerable range.

[0099] The “parallel movement mode” is an operation mode in which drivesources provided independently on the left and right sides arespeed-controlled to drive left and right wheels at the same speed aseach other for a parallel movement of the moving rack. The “obliquemovement correction mode” is an operation mode in which the rotationalspeed of the drive wheel on the side of the moving rack moving ahead inthe moving direction is lowered, or in which that of the drive wheel onthe side moving behind is increased.

[0100] Referring now specifically to FIGS. 30 to 33, two adjacent racksare each identified generally by the same reference numeral 101. In FIG.30 the rack 101 on the right side is in the desired postureperpendicular to its moving direction and without any oblique movement.However the rack 101 on the left side is moving obliquely or skewed withrespect to the moving direction. Each moving rack 101 is provided with adrive 63 and drive motors 59, as previously described. The samereference numerals are used to identify these components as previouslyapplied in as much as these components are the same as previouslydescribed. The motors 104 59 are speed-controlled to be driven forrotation at the same speed as each other by any suitable control meansfor the parallel movement of the racks 101. This operation mode is the“parallel movement mode” previously mentioned.

[0101] The two racks 101 are associated with two reference bodies 102that extend in the moving direction of the racks 101 and are parallel toeach other at a given interval. The reference body 102 has the samefunction as the reference body in the foregoing embodiments and may beprovided below the moving rack 101, that is, on the floor on which themoving rack is installed, or above the moving rack 101. In theillustrated example, it is provided above the moving rack 101.

[0102] Each moving rack 101 has a pair of sensors 103 and 104 fordetecting displacement with respect to one of the reference bodies 102.For the detection method of the sensor 103 and 104 in this embodiment, amechanical sensors of the same principle as the mechanical sensor shownin FIGS. 24-29 is used, but the invention is not so limited.

[0103] That is and as shown in FIG. 32, referring to one of the sensors,103, it has a fixed member 105 fixed to the moving rack 101 and a leverrising up for swinging movement from the fixed member 105 and biasedsuch that a roller 106 at the top is in contact with one side surface ofthe reference body 102. The other of the sensors, 104, likewise, has afixed member 107 fixed to the moving rack 101 and a lever rising up forswinging movement from the fixed member 107 and biased such that aroller 108 at the top is in contact with one side surface of thereference body 102.

[0104] The paired sensors 103 and 104 are disposed at the front and therear of the moving rack 101 at a given spacing. These sensors 103 and104, like the mechanical sensors in the foregoing embodiment, have avariable resistor whose resistance value changes in response to theinclination angle of the lever, and this constitutes a potentiometerarranged such that the output voltage changes in response to theinclination angle of the lever.

[0105] If a moving rack, like the moving rack 101 shown in FIG. 30 onthe right side, is perpendicular to the reference body 102 withoutinclination, the paired sensors 103 and 104 have the same posture asshown in FIG. 31 and the levers of the sensors stand approximatelyupright. Therefore, the difference in output between both sensors isapproximately 0 V.

[0106] On the other hand, if a moving rack is, like the moving rack 101shown in FIG. 30 on the left side, inclined with respect to thereference body 102 because of its oblique movement, the both levers ofthe paired sensors 103 and 104 are inclined in a certain direction asshown in FIG. 32. However, since the paired sensors 103 and 104 aredisposed at a certain distance apart in the moving direction, theamounts of inclination of the levers of the paired sensors 103 and 104differ, causing a difference in output between the both sensors 103 and104. Then, if the output of one of the sensors is subtracted from thatof the other, the direction of the inclination of the moving rack can bejudged from the subtraction result, which is plus or minus, and themagnitude of the inclination from the difference in output between theboth sensors.

[0107] Thus, in this embodiment, the amount of inclination of the movingrack which can be detected from the outputs of the sensors, that is, theamount of oblique movement is detected, and if the amount of obliquemovement detected is within a tolerable range, the left and right drivesources are controlled independently in the foregoing “parallel movementmode.” Also, if the amount of oblique movement detected is beyond thetolerable range, the left and right drive sources are controlledindependently in the foregoing “oblique movement correction mode” toeliminate the oblique movement. Specifically, the motors 59 disposedindependently on the left and right sides of the moving rack arecontrolled such that the side moving behind moves faster than the sidemoving ahead. The motor on the side moving ahead may be decelerated, themotor on the side moving behind may be accelerated, or speeds of theboth motors may be simultaneously controlled.

[0108] In the embodiment described above, since, when the moving rack isdriven in the “parallel movement mode,” the rotational speeds of themotors are kept constant and control of accelerating/decelerating theleft and right sides of the moving rack 101 is not performed, the movingrack 101 moves smoothly without jerk. If oblique movement is within atolerable range, the moving rack still makes a parallel movement whilemaintaining the oblique movement within a tolerable range.

[0109] Even if the moving rack 101 moves obliquely because of biasedloading after repeated reciprocating movements, the moving rack isdriven in the “parallel movement mode” as long as the amount of obliquemovement detected is within a certain tolerable range. It is not untilthe amount of oblique movement is beyond the certain tolerable rangethat control operation is performed in the “oblique movement correctionmode” to eliminate the oblique movement.

[0110] If the oblique movement is corrected to within the tolerablerange, the moving rack is driven again in the “parallel movement mode.”Here, it is preferable that a hysteresis is provided between theswitching point from the “parallel movement mode” to the “obliquemovement correction mode” and that from the “oblique movement correctionmode” to the “parallel movement mode.” For example, it is preferablethat, if oblique movement is beyond a certain tolerable range, controlis switched over to the “oblique movement correction mode,” and that, inthe “oblique movement correction mode,” control is not switched over tothe “parallel movement mode” immediately when the oblique movement fallswithin the tolerable range, but is switched to the “parallel movementmode” when the oblique movement is practically eliminated.

[0111] In a moving rack having an optical passage ingress sensor, it ispreferable that the maximum value of the amount of oblique movement atwhich switching over to the “oblique movement correction mode” is to beperformed is set to the amount of oblique movement within a range inwhich the optical passage ingress sensor can fulfill its function.

[0112] Referring now to FIG. 33 shows an example using an opticalpassage ingress sensor to determine if a person or object moves betweentwo adjacent partitions. In such an arrangement In FIG. 33, lightemitting sections 111 are placed on the opposing faces of adjacentmoving racks 101, 101 for emitting a light beam from one moving rack 101toward the other moving rack 101. Facing these light emitting sections111 on the opposing faces of the other moving racks 101 are disposedlight receiving sections 112 for receiving the light beam. In theexample of FIG. 33, on one of the left and right ends of the moving rack101 is disposed the light emitting section 111 and on the other end thelight receiving section 112.

[0113] If a person(s) or other obstacles enter the working passageformed between the two moving racks 101, 101, the light beam is blockedby the person(s) or other obstacles, and the ingress of the person(s) orother obstacles can be detected. Safety can be secured if all the movingracks are emergency-stopped in response to this detected signal. Such anoptical passage ingress sensor has been known in the art of the movingrack, and the detailed description will be omitted.

[0114] For the optical passage ingress sensor to fulfill its function,it is required that a light beam emitted from a light emitting section111 on one moving rack 101 can be received by a light receiving section112 on the other moving rack 101. However, if the amount of obliquemovement of the moving rack becomes large, the light axis of the lightbeam emitted from the light emitting section 111 deviates, and the lightreceiving section 112 will fail to receive the light beam. This producesthe same result as when the light beam is blocked by a person(s) orother obstacles, resulting in an emergency stop of the movements of allmoving racks.

[0115] In addition, to return to a normal condition from theemergency-stopped state, the oblique movement of the moving rack needsto be corrected, for example, by human power, which is a troublesomework. Therefore, in accordance with another feature of the inventioncontrol is set such that it is switched over to the “oblique movementcorrection mode” if a certain amount of oblique movement is detectedbefore the light receiving section 112 fails to receive the light beamfrom the light emitting section 111.

[0116] The optical passage ingress sensor may be arranged such that alight emitting section and a light receiving section are provided onlyon one moving rack, that a light beam emitted from the light emittingsection is reflected by a mirror on the other moving rack, and that alight receiving element mounted thereon receives the reflected lightbeam.

[0117] Thus from the foregoing description it should be readily apparentthat the described embodiments provide moveable partitions and controlsthat permit smooth operation and parallel movement even when they aretrackless and that provide safety in operation in avoiding encounterswith unexpected objects without unnecessarily stopping the operationwhen an object is not actually there. Of course those skilled in the artwill readily understand that the described embodiments are onlyexemplary of forms that the invention may take and that various changesand modifications may be made without departing from the spirit andscope of the invention, as defined by the appended claims.

1. A method of controlling the movement of a moveable partition havingat least a pair of transversely spaced, ground engaging drive elementsfor moving the partition along a parallel path, said method comprisingthe steps of sensing the path of movement of the partition andcontrolling the drive elements to maintain a parallel path of movement.2. A method as set forth in claim 1 wherein the drive elements aredriven at the same rate as long as the path of movement is parallel. 3.A method as set forth in claim 2 wherein the drive elements are drivenat the same rate as long as the path of movement does not deviate fromparallel by more than a predetermined amount.
 4. A method as set forthin claim 3 wherein the drive elements are driven at a different rateonly if the path of movement deviates from parallel by more than thepredetermined amount.
 5. A method as set forth in claim 2 wherein adetector is provided to determine if an undesired object is in the pathof the partition and separately controlling the drive elements inresponse to an apparent detection to shift the partition to see if thedetection was an error caused by the orientation of the partition and ifthe condition still exists after a predetermined correction the movementof the partition is halted.
 6. A method of controlling the movement of amoveable partition having at least a pair of transversely spaced, groundengaging drive elements for moving the partition along a parallel path,said method comprising the steps of sensing optically when an objectmoves into the path of movement of the partition and separatelycontrolling the drive elements in response to an apparent detection toshift the partition to see if the detection was an error caused by theorientation of the partition and if the condition still exists after apredetermined correction the movement of the partition is halted.
 7. Amoveable partition having at least a pair of transversely spaced, groundengaging drive elements for moving said partition along a parallel path,a sensor for sensing the path of movement of the partition and a controlresponsive to the output of said sensor to differently operate saiddrive elements to maintain a parallel path of movement.
 8. A moveablepartition as set forth in claim 7 wherein the sensor comprises anoptical sensor cooperating with a path guide fixed relative to thepartition.
 9. A moveable partition as set forth in claim 7 wherein thesensor senses the amount of deviation from the parallel path and onlyoperates the drive elements separately if the deviation is greater thana predetermined amount.
 10. A moveable partition as set forth in claim 7wherein an optical sensor provides an indication that an undesiredobject is in the path of the partition and stops the drive elements ifan object is detected.
 11. A moveable partition as set forth in claim 10where the control first operates the drive elements differently and ifthat does not stop the detection the drive elements are stopped.
 12. Amoveable partition as set forth in claim 7 wherein the sensor is amechanically actuated position sensor and provides a signal indicativeof the actual position and only operates the drive elements separatelyif the deviation is greater than a predetermined amount.
 13. A moveablepartition as set forth in claim 1 wherein the partition is supported ona floor and an overhead safety hanger is provided that does not supportthe partition or interfere with its operation unless the partitionbecomes unbalanced and may fall.
 14. A moveable partition as set forthin claim 13 wherein the sensor is a mechanically actuated positionsensor and provides a signal indicative of the actual position and onlyoperates the drive elements separately if the deviation is greater thana predetermined amount.
 15. A moveable partition as set forth in claim14 wherein the mechanically actuated sensor has an element engaged withthe safety hanger.
 16. A moveable partition as set forth in claim 15wherein the mechanically actuated sensor senses the actual positionrelative to the safety hanger.
 17. A moveable partition as set forth inclaim 16 wherein there are a pair of safety hangers and there is amechanically actuated sensor associated with each safety hanger.
 18. Amoveable partition as set forth in claim 17 wherein the drive elementsare driven at the same rate as long as the path of movement does notdeviate from parallel by more than a predetermined amount.
 19. Amoveable partition as set forth in claim 17 wherein the drive elementsare driven at a different rate only if the path of movement deviatesfrom parallel by more than the predetermined amount.
 20. A moveablepartition as set forth in claim 7 wherein there sensor comprises atleast a pair of spaced optical sensors.
 21. A moveable partition as setforth in claim 20 wherein the pair of optical sensors are spaced alongthe width of the partition.
 22. A moveable partition as set forth inclaim 20 wherein the pair of optical sensors are spaced along thepartition in its direction of travel.